1. Field of the Invention
The invention relates to a pushbutton actuated overload protection switch, and in particular to an instant-on, manually, thermally and/or electromagnetically tripped onboard protection switch.
2. Brief Description of the Prior Art
An overload protection switch of the above noted type is known from German Patent No. 21 23 765. Its switch housing, comprising an upper and lower housing part, is penetrated by a switch rod having the pushbutton on its outer end and displaceably supported in the direction of pressure and acted upon by a pushbutton spring counter to the ON direction. A toggle lever, comprising two levers connected at their inner ends via a rotary slide joint, is disposed in the switch housing, between the switch rod and the contact bridge, and the contact bridge is embodied as a two-armed lever extending in the ON direction approximately at right angles to the displacement direction of the switch rod and joining the counterpart contact elements that are secured to the housing to one another. The first lever of the toggle lever, oriented toward the switch rod, is embodied as a bell crank and is supported pivotally and substantially displaceably in the direction of rotation of the switch rod in first grooves of the switch housing, by means of a bearing bolt disposed in the vicinity of the apex of the crank. With its free end, this first lever of the toggle lever is also braced, counter to the ON push direction of the switch rod, on a detent lever which is adjustable by a thermal and/or electromagnetic trip, such that the toggle lever can be spread apart into its stretched position from the ON push motion of the switch rod. In the ON position, the toggle lever is fixable in the housing by means of a detent pawl, with a substantially stretched toggle lever position. In the switch according to German Patent No. 21 23 765, this detent pawl is a one-armed lever supported on the side of the first lever of the toggle lever remote from the detent lever, and the one-armed lever, by the tension of an OFF spring fastened between it and the bell crank, latches in with the bearing bolt of the bell crank and fixes the bell crank in the ON position.
The second lever of the toggle lever, remote from the switch rod, carries the contact bridge on its free end, by means of a joint formed by a bolt; the bolt is guided in second grooves in the housing that extend in the push direction of the switch rod. These grooves have a detent that is operative counter to the push direction of the switch rod; at this detent, upon its forward motion into the 0N position of the contact bridge, the bolt is supported briefly prior to attaining the ON position, before being pressed out of the detent, by the pivoting motion of the second lever which is associated with the further spreading motion of the toggle lever, and is pressed abruptly by a contact spring into the ON position of the contact bridge. The instantaneous switching ON of the switch latch is thereby assured.
The aforementioned OFF spring is secured with one end to the inner end of the first lever that protrudes beyond the joint of the toggle lever. At its other end, it is eccentrically supported on the detent pawl in such a manner that it urges the toggle lever in its buckling direction and hence in the OFF direction. The detent pawl itself is simultaneously pressed in the direction of its position that acts upon the bearing bolt for the first lever of the toggle lever.
The switch according to German Patent No. 21 23 765 is switched ON by the push actuation of the pushbutton and switched OFF by the pull actuation of the pushbutton. By pulling the switch rod counter to the spring force of the OFF spring, the detent pawl is pivoted out of its locking position, such that the first lever is yanked by the OFF spring in the opening direction of the switch latch. This causes the toggle lever to buckle inward and raises the contact bridge from the counterpart contacts attached to the housing.
Push-pull actuation is disadvantageous from the standpoint of ease of use and safety, because two different actuation directions are required for switching it ON and OFF. For rapid switching OFF, push actuation of the switch would be desirable as well, because in that case the pushbutton need not be awkwardly grasped first.
Accordingly, it is the object of the present invention to further develop the overload protection switch according to the prior art in such a way that it is switched both 0N and OFF by a push actuation of the pushbutton.